Gyroscope systems often incorporate level sensors for maintaining an inertial reference member (stable reference platform gimbal) level and stable about its roll and elevation axes with a high degree of accuracy. Such level sensors use electrolytic switches which are accurately mounted in relation to the stable reference platform gimbal.
A level sensor including an electrolytic switch is desirable for the purposes described since this type switch has a high sensitivity, is low in cost, and is highly reliable due to an absence of moving parts. One such gravity type switch is referred to in the art as a "bubble switch". Although the electrolytic switch is capable of maintaining almost constant null voltage under steady state temperature conditions, it is sensitive to ambient temperature conditions.
As is well known in the gyroscope art, to precess the spin axis of the gyroscope about one axis, a torque must be applied at an axis at perpendicular angle to the first axis. Thus, for example, to maintain the spin axis of a directional gyroscope in a horizontal position, a torque is applied about the vertical axis. Conventional practice has been to mount liquid level switches on the various gimbal rings to sense the tilting of the gimbal from a desired position and energize a corresponding precessing device (motor) to return the gimbal to the desired position.
In conventional liquid level switches, a fluid electrolyte moves from one position in the switch to another as the gimbal is tilted. For example, if such a switch be mounted on the normally horizontal gimbal of a direction gyroscope, a tilting about the horizon causes the switch to tilt and operate a precessing device to apply a torque about the vertical axis to restore the gimbal ring to a level horizontal position.
Demand for rapid arming of unmanned flight vehicles (missiles and drones) has created a need for fast initial erection rates for vertical gyros. Limited battery power has imposed stringent power requirements and the need for a DC power torquer system. DC torquer components are bulky and costly as compared to AC torquer systems, but it is much more difficult to exercise precise control over an AC system than it is over a DC system.
Electronic systems have previously been applied to control gyroscope erection systems. One prior art gyroscope erection system uses a control circuit to cut out the erection system during rapid attitude changes. This system is described in U.S. Pat. No. 3,203,261.
It is therefore desired to use electronics to create a vertical gyro erection system that uses a DC power supply, generates fast erection rates, has high performance gyro accuracy, and uses simple AC torquer motor components.